Removable and lockable guide ring in an orifice passing through a plate and its use for a guide tube of a nuclear reactor

Abstract

Removable and lockable guide ring in an orifice passing through a plate and its use for a guide tube of a nuclear reactor. The guide ring comprises a tubular body (25), one part (25a) of which is introduced into the orifice (22) in the plate (20). A second part (25b) of the tubular body (25) comes up against the plate (20), and claws (40) having the form of being levers, for attaching the ring (21) to the edges of the orifice (22), are mounted freely in the tubular body (25). A spring (45) makes it possible to return the claws (40) into the attachment position. The invention applies particularly to a guide tube of a pressurized-water nuclear reactor.

I claim: 
     
       1. Removable and lockable guide ring in an orifice passing through a plate, an internal bore of the guide ring and the orifice in the plate being coaxial relative to one another, and comprising an integral tubular body a first, lower part of which enters the orifice in the plate and a second, upper part of which rests on one of the faces of the plate around the orifice, means of attaching the ring to the edges of the orifice on the face of the plate opposite the face on which the tubular body rests, and an elastic means of returning the attachment means into an attachment position for locking the ring in the orifice in the plate, wherein the attachment means comprising at least two claws each having the form of a bent lever having a first arm an end of which comprises an attachment end, and a second arm forming a predetermined angle relative to the first arm, the claws being mounted freely relative to the tubular body and being held in the tubular body by the elastic means, comprising at least one spring inserted between one part of the tubular body and the second arm of the claws, so as to push the attachment ends of the claws in the radial direction towards the ouside of the tubular body, and wherein said at least one spring is located entirely below said second arm. 
     
     
       2. Guide ring according to the claim 1, wherein the arms of the claws form an angle of approximately 90 degrees. 
     
     
       3. Guide ring according to claim 1, wherein the plate is an end plate of a guide tube of a control rod of a pressurized-water nuclear reactor, the ring having an internal bore for guiding a follower attached to the control rod. 
     
     
       4. Guide ring according to claim 1, wherein the wall of the tubular body has passing through it, in its first part, at least two apertures each communicating with a groove extending in the axial direction of the ring towards the second part of the tubular body, a lateral wall of which has at least two ports passing through said lateral wall in circumferential positions in line with the grooves, a claw being received in a housing comprised of an aperture, a groove and a port placed in line with one another in said axial direction, the first arm of the claw being received in the groove, and the second arm passing through the port to project in the radial direction outside the tubular body. 
     
     
       5. Guide ring according to claim 4, wherein the grooves open into the second part of the tubular body in an annular recess containing the spring. 
     
     
       6. Guide ring according to claim 5, further comprising a piece fastened rigidly to the tubular body to close off the annular recess containing the spring. 
     
     
       7. Guide ring according to claim 4, wherein the aperture passing through the wall of the first part of the tubular body has the form of a cylinder whose axis is inclined relative to the horizontal cross-section of the guide ring, and, on the same side as the outer surface of the first part of the tubular body, is continuous with an axially extending rectangular slot whose width is equal to the diameter of the cylindrical aperture, the end part of the claw having a cylindrical form and dimensions corresponding to those of the aperture, so that, under the action of the spring, the end attachment part of the claw is introduced into the slot, on which the end of the attachment part bears radially when the guide ring is in its locking position. 
     
     
       8. Guide ring according to claim 7, wherein the end attachment part has a bearing and attachment surface of convex form corresponding to the shape of a concave part of the profile of the lower surface of the plate around the orifice.